Waste-heat recovery system

Abstract

A waste-heat recovery system for a waste-heat source, made up of an ORC (Organic-Rankine Cycle) postconnected thereto. The waste-heat source is connected with the heating device of the ORC as well as an expansion machine, coupled to a generator, for steam expansion in the ORC, which has magnetic bearings with an associated control device and a power supply via a direct current intermediate circuit of a generator frequency converter. The design and safe operating behavior of a waste-heat recovery system made up of an ORC post-connected to a waste-heat source are optimized. In a power supply failure, the electric energy that a down-running generator continues to generate is used to supply the magnetic bearings with the associated control device in order to ensure a safe operation in the event of a power supply failure.

What is claimed is: 
     
       1. A waste-heat recovery system for a waste-heat source, comprising:
 an ORC (Organic-Rankine Cycle) postconnected with respect to the waste-heat source, the ORC including: 
 a heating device connected to the waste-heat source, 
 a down-running generator, and 
 an expansion machine coupled to the down-running generator and for performing a steam expansion, the expansion machine including magnetic bearings, with an associated control device and a power supply via a direct current intermediate circuit of a generator frequency converter, wherein in the event of a power supply failure, an electric energy that the down-running generator continues to generate is used to supply the magnetic bearings with the associated control device. 
 
     
     
       2. The waste heat recovery system as recited in  claim 1 , wherein, in the power supply failure, the electric energy that the down-running generator continues to generate and which cannot be fed into a power supply system and is not required to supply the magnetic bearings with the associated control device is stored in the direct current intermediate circuit. 
     
     
       3. The waste heat recovery system as recited in  claim 1 , wherein, in the power supply failure, the electric energy that the down-running generator continues to generate that cannot be fed into a power supply system and is not required to supply the magnetic bearings with the associated control device is stored in the direct current intermediate circuit in that a voltage in the direct current intermediate circuit is raised briefly. 
     
     
       4. The waste heat recovery system as recited in  claim 1 , wherein in the power supply failure, the electric energy that the down-running generator continues to generate is output into the direct current intermediate circuit via a frequency converter coupled to the down-running generator, to be fed into a power supply network. 
     
     
       5. The waste heat recovery system as recited in  claim 1 , wherein an excess electric energy that the down-running generator continues to generate that is neither fed into a power supply network nor required to supply the magnetic bearings with the associated control device, and that is also unable to be stored in the direct current intermediate circuit, is reduced via at least one electric brake resistor. 
     
     
       6. The waste heat recovery system as recited in  claim 1 , further comprising a voltage-monitoring device at a frequency converter for feeding into a network for a voltage in the direct current intermediate circuit. 
     
     
       7. The waste heat recovery system as recited in  claim 6 , wherein the voltage-monitoring device at the frequency converter for a power supply feeding compares a current voltage in the direct current intermediate circuit to a specifiable maximum value, and connects at least one electric brake resistor if the current voltage has been one of reached and exceeded.